I have Poke berries ready to pick. I don't know how to separate the seeds from the juicy berry except dry the berry. The berry doesn't totally dry enough to put them into little plastic bags with out them molding.
I've never had any experience with poke seeds (yet), but they look quite similar to seeds from malabar spinach and papaya seeds from what I could see. I put those in a small colander and using my hand rinse them under running water to remove the 'fleshy part' off of them, then put them out on paper toweling to dry. It's messy but it works. Hope that helps. :)